public class ConstantDemo {
	
	
	public static void main(String[] args) {
		
		// ?????f?????
		
		// 1. ?????
		System.out.println("hello");
		System.out.println("world");
		System.out.println("??");
		// 2. ????
		System.out.println(100);
		
		// 3. ????
		System.out.println(100.22);
		// 4. ????
		System.out.println('A');
		System.out.println('a');
		// 5. ????
		System.out.println(true);
		System.out.println(false);
		// 6. ???
		System.out.println("null");
	}
}